1. Field of the Invention
This invention relates to Mn-containing Co-based near-zero magnetostrictive metallic glasses having high saturation induction.
2. Description of the Prior Art
Glassy metal alloys (metallic glasses) are metastable materials lacking any long range order. They are conveniently prepared by rapid quenching from the melt using processing techniques that are conventional in the art. Examples of such metallic glasses and methods for their manufacture are disclosed in U.S. Pat. Nos. 3,856,513, 4,067,732 and 4,142,571.
These patents disclose metallic glasses having excellent soft magnetic properties. One such property, saturation magnetostriction (.lambda..sub.s) is related to the fractional change in length that occurs in a magnetic material magnetized to saturation from the demagnetized state. The value of .lambda..sub.s, a dimensionless quantity, is usually quoted as the fractional change in length in parts per million (ppm). Henceforth, .lambda..sub.s will be referred to simply as "magnetostriction".
Ferromagnetic alloys having low (near-zero) magnetostriction are disclosed in U.S. Pat. No. 4,038,073. That patent teaches that a combination of high permeability and high saturation induction in near-zero magnetostrictive metallic glasses would find use in a great variety of applications, especially in magnetic recording heads, over a wide frequency range.
Manganese containing metallic glasses, having near-zero magnetostriction and high saturation induction have been disclosed in German Offenlegungschrift No. 30,21,536, published Dec. 12, 1980 and European Patent Application No. 0,021,101, published Jan. 7, 1981. These patent applications teach that the presence of manganese tends to yield a metallic glass wherein the crystallization temperature is above the ferromagnetic Curie temperature. The preferred compositions disclosed by the aforementioned patent applications are depicted in FIG. 1 by the shaded areas, the dashed line and the black dot.
The highest values of saturation induction previously reported for near-zero magnetostrictive metallic glasses having high permeability (greater than 5,000 at a frequency of 1 kHz and an induction level of 0.01 Tesla) are about 100 emu per gram, or about 1 Tesla (T). New applications, such as recording heads used with metallic tapes require magnetic materials having saturation induction higher than 1 T. In other applications, such as switch-mode power supplies, saturation induction higher than 1 T is necessary to accommodate the requirements for miniaturization of electronic components.